Electric high-tension switching system and apparatus



rll. fili G. A.,BURNHAM Filed Dec.vl3. 1927 2 Sheets-Sheet l ELECTRICHIGH TENSION SWITCHING SYSTEM AND APPARATUS l l l Feb. 25, 1930.

Feb. 25, 1930. G, A, BURNHAM y 1,748,060

`:IIJEGTRIC HIGH TENSION SWITCHING SYSTEM AND APPARATUS Filed D90. 15.192'? 2 Sheets-Sheet 2 Patented l Feb. 25, 1930 uNrrlsD STATES PATENTOFFICE GEORGE A. BURNHAM, F SAUGUS, MASSACHUSETTS, ASSIGNOR T0 CONDITELECTRI- CAL MANUFACTURING CORPORATION, OF SOUTH BOSTON, MASSACHUSETTS,A COR- PORATIOISIl OF MASSACHUSETTS ELECTRIC HIGH-TENSION SWITCHING-SYSTEM AND APPARATUS Application led December 13, 1927. Serial No.239,790.

This invention relates to electric high tension switching systems andapparatus wherein the high tension buses, usually extended di rectlyfrom the generators, are contained 1n 5 ducts and are extendedimmediately above or beside oil immersed switches which are con nectedwith the buses and also with branch lines which they control. When oilswitches are opened under heavy .loads or under a short circuit, heatedoil and flame are frequently expelled from the switch casings. If theheated vapor or flame comes in contact with the high tension buses itforms a sutilciently low conducting path between them tol cause adisastrous arc to form. Since the buses usually are directly connectedwith the generators without interposed overload circuit breakers thereinthere is no way of quenching the are and removing the short circuit fromthe buses. The arc can thereupon continue indefinitely and cause greatdamage to the station and cause a loss of service extending over manyhours. As a consequence, the buses are usually enclosed in the aforesaidducts to shield them from contact with conducting gases that may beexpelled from the switches.

There are a number of types of bus enclosing systems. In one type, theduct in which the bus is contained is filled with oil which serves notonly to shield the bus from contact with gases butalso to provide theinsulation for the bus. With this system, however, the duct must be madeand kept absolutely oil l tight, otherwise the oil will leak out andremove the insulation from the`bus so that a flash over will occur fromthe bus to the duct, which usuall is made of metal. Danger from fire,due to tlvxe ignition of the oil in the duct from aL possible flashover, is always present. When 'a flash over occurs large volumes ofexplosive gases and vapors and free carbon may e generated; andthese mayexplode and do great damage. e

In another type of .bus structure the oil is replaced by ain insulatingcompound .which is pouredinto the ductwhile hot and liquid and cools andsolidiies about the bus and thus forms a hard and brittle insulatingcompound. Danger of leakage of the insulating conductingwalls of theduct.

valso removed therefrom,

compound is thus obviated but the fire hazard is not greatly reduced.Since the compound is brittle, it has a tendency to crack when subjectedto strains and thus open up a path for a flash-over arc. The arc setsfire to the compound and it burns, with disastrous results.

In yet another system of bus structure, tl1e\ bus is contained within aduct which contains no especial insulating material,y and the duct ismade suiiciently large inI cross section to prevent flash over betweenthe bus and the With this type of structure, it has been found that hotgases discharged from the switch will be forced into the duct throughseemingly minute crevices and channels between the walls thereof andcause the formation of an arc between the bus and the dpct. In someinstances, it has'- been found that the interior walls of the ductandthe insulators on which the bus is mounted become coated with carbonexpelled from the oil switch and that the carbon provided aconductingpath which caused a flash over and I the failure of theswitching system.

` present invention to It is an object of the provide a switching systemof the type above set forth with a bus structure yat the oil switches soarranged that gas expelled from the switch can not vcome in contact withthe bus; and also so arranged that the troubles ,B0 and defects of theabove enumerated present systems are absent. It is a further object ofthe invention to rovide an electrical switchi lng system and a usstructure therefor wherein the bus is enclosed in an insulating body 85that is not affected by arcs, will not burn or i give'oilt' gases, andis mobile so that it can conform itself to changes in shape ordimensions vof the bus and enclosing structures due to expansion,distortion and the like and o0 also so that it can be poured orotherwise placed readily inthe bus-enclosing duct and and, while beingfreely mobile, yet has such characteristics that only the materialimmediately at large openings in the duct will escape, while none i willescape through small openings. I

It is a further object of the 'invention to provide an electricalswitching system composed of oil immersed electric switches and an .100

sion circuit. A. platen or carriage 14 is verf enclosed bus structureassociated with the switches, with a loose, solid filler in the busducts which is composed of discrete, solid, electrically-insulatingparticles which surround and enclose the bus and prevent the gasesdischarged from the oil switches vfrom penetrating the fillersufficiently to come in contact with the bus and cause trouble.

It isa yet further object of the invention to provide an electricalvswitching apparatus wherein the buses are enclosed incompartmentsand'wherein the compartments contain sand. in which the buses aresubmerged.

A further object of the invention is generally to improve theconstruction and operation of high tension electric switching systems.

Fig. 1 is a front elevation of a switching system embodying the presentinvention.

Fig. 2 is a sectional view taken along line 2-2 of Fig. 1.

Fig. 3 is a sectional detail of the contact structure between the switchterminals Vand the bus terminals.

Fig. 4 is a perspective view of a bus duct embodying the invention.

Fig. 5 -1s a longitudinal sectional elevation through a bus ductembodying the invention.

Fig. 6 is a perspective detail showing a modied form of bus duct.

Fig. 7 is a sectional detail illustrating the manner in which the sandfiller is retained in the duct about an opening therein.

Figs. 1 and 2 `illustrate my invention applied to a three phaseswitching apparatus. As shown in these figures, the ap aratus includes aframe having theJ base or door 10 and the -laterally-spaced verticalside walls 12 which form thr'ee cell enclosures a, b, c, respectively,for the three phases'of a high tentically movable between and is guidedby the walls 12 of e'ach cell on a vertically screw threaded shaft 16which' is operated by suit- Iable mechanism 18 from a control shaft 20to raise and lower the carriage or platen. I An oil immersed electricswitch 22 of any suitable type is received in an opening in each platenand is supported thereon by the feet 24., The platen can be raised toelevate the switch into an'operating. position as shown in Fig. 2 and itcan also be lowered to lower the switch so thatit is supported byits.wheels 26 on the floor 10 of the cell and thus can be moved out of thecell and away from the platen for inspection or otherwise.

The terminals 28 of the switch extend vertically thereabove and areprovided with vertical contact blades 30 for engagement with the busterminals hereinafter to be described. insulating cups 32 surround saidterminals and upstand thereabove and are intimately connectedmechanically therewith and are'` adapted to contain oil in which thecontact blades and also the terminals of the buses are adapted to beimmersed, thereby to shield the live partsl of thecontact structurefromaccess by the hot gases expelled from the' switch. The cups 32 areprovided with depending annular iianges 34 which surround the upper endsof the insulators of/the switch l terminals for the same reason.

Brackets 36 are carried by and upstand i lshelves 38. The enclosingducts or compartments can have any suitable construction but, as hereshown, are formed of side and bottom walls 54 secured to longitudinallyeX- tended corner angles V56. Each duct is provided with a cover 58which is removable for access to the interior of the duct. No especialcare is taken to make the ducts absolutely iuid tight. The ends of theducts are provided with outstanding ianges 59 by which horizontallyaligned ducts of adjacent switching systems can be attached thereto. Thebuses are mounted in the middle of the ducts on suitable insulators 60which are carried by the bottom walls of the ducts. Each of the buses isprovided with branch'leads 42a, 44a, and 46a which are extended throughthe middle of openings 62 in the front` :walls of theV ducts land intovertical branch ducts 48a, 50a, and 52a which are disposed in front ofthe main ducts and abovethe switches. The

branch ducts are constructed in the same manner as the main ducts andhave removable top walls or` covers and openings' in their rear wallswhich register with the openings in the main ducts; and said openingsare practically the full height of the main ducts. Insulating bushings64 are extended through the bottom walls of the branch ducts, in themiddle thereof, and have their upper ends connected with the branchbusesand have spring pressed contactvjaws 6 6 at their lower ends whichare adapted to be engaged by the contact blades 30 of the switchterminals thereby to connect the switches electrically with the buses.Small compartments or pot heads 68 which may be similarly constructed.to the bus ducts are located immediately underthe line 4of bus ductsand in the rear and in line with the branch ducts and above the rearswitch terminals. Insulating bushings 70 are extended through the middleof the bottom walls of said potV heads and are. adapted to be connectediso electrically with the rear terminals of the switches.

Branch line cables 7 2 extend upwardly from the rear of the switchingframe and have their lead sheaths secured in a fluid tight manner to thedepending and rearwardly extended necks 69 of said pot heads while theinsulated portion of the cable extends into the middle of the pot headsand is electrically connected to the upper ends of the bushings therein.

In accordance with this invention, the electric conductors are locatedin the middle of the ducts or enclosing compartments and the distancebetween the conductors and the side walls of the ducts which are made ofmetal is adapted to be sufliciently great to provide a suitably highfactor of safety against flashover when the ducts are filled with air.

As above stated when the oil immersed switches open under severeoverload or on short circuit, they sometimes expel into the surroundingatmosphere hot oil, vapors, gases, fume and flame which if allowed tocome in contact with the high tension buses or conductors will cause aflash over between the buses and the casings and the enclosing ducts andthereby often cause Great damage and extended loss of service.onsequently, and in accordance with this invention, I ll the ducts witha loose, electricall reproof body 80 which complete y surrounds theducts and provides an effective barrier against access of heated gasesand conducting particles expelled from the switch thereto. Also, inaccordance with this invention, the above 'described body is composed ofsand which is the best material known to me at present. Sand hasproperties which are of particular value in connection with thisinvention. Sand is lreproof, and will not burn as oil does. The sandoccupies the ducts as a loose body 80, and can be easily removed fromthe duct if it is desired to replace the bus with one of differentcurrent carrying section, or for other reasons. The sand can also be putinto the ducts when the covers thereof are removed without any especialtools or without the exercise of any especial care exce t to see thatthe ducts are full. The branch ucts and pot heads are also filled withsand so that all bare high tension conductors are completely submergedin the sand. It is not necessary to exercise extreme diligence insealing the ducts against small cracks or crevices as is the case withoil because the sand will not leak out of small crevices since itbridges them over and forms an arch which prevents the sand from fallingout. Even though the crevices or openings are unduly large or a holeisburned in the bottom wall of a duct b some extraneous arc, the damageis slight fbr, because of the relatively steep angle of res ose of thesand, thesand on each side of t e opening,

as the opening 82 of Fig. 7, will assume the slope 84so that only thesand immediately above the opening will be lost while the remainder ofthe sandin the duet will remain in place. The sand is effective in.preventing hot gases from reaching the bus for the sand cools the gasesas they flow therethrough so that they are cooled below a point at whichthey are deleteriously conducting before they have penetrated the sandbody to any harmful distance. Furthermore, the sand body ol'ers greatresistance to the flow of gas thereinto, and so also prevents access ofgas to the bus. If oil or carbon is blown into the duct through smallcrevices or channels the oil and the carbon are entrapped in the voidsbetween the small discrete particles of sand at the outermost surfacesof the sand body and so can not penetrate to the interior of the sandbody. Sand is a good electrical insulator. It also provides mechanicalsupport for the bus at all points along its length so that fewerinsulating supports for the bus are needed and the bus is restrained bythe sand from being forced out of its original position by strongmagnetic forces acting lupon it as is often the case. Should anabnormally high potential be impressed upon the bus and an arc occurthrough the sand to the wall of the duct, no permanent damage lwill bedone since the sand particles can move in to close any void formed bythe arc; although experiments have failed to disclose the presence of anvoid. The sand also acts as a cooling medlum and tends to cool the arcand quench it so that the arc has a strong tendency to go out when thevoltage of the bus is lowered. The presence of sand also prevents theformation of corona in the space between the bus and the duct at a valueof potential4 that would cause corona in air. This is due to the greaterdielectric capacity of the sand over that of air so that theelectr'ostatic flux passes through the sand particles rather than in thea1r filled voids between them.

Preferably, the sand is a quartz sand and free from conductingparticles, or metallic compounds, as an iron compound, although itappears that sand containing some amounts of iron oxide or other ironcompounds usually found in sand gives satisfactory results. Sand taken;from many sources, and sand of various grades of iineness, beach sandand sand approximating in size line gravel, seemtoperformvabout-equallywell. Preferably,the sand should be free fromsilt or decayed vegetable matter and foreign substances. The dimensionsofthe sand particles can vary within rather wide limits. I have foundthat sand particles j mm. in thickness give satisfactory results.Preferably, the sand should be of sufficient fineness so that corona inthe air spaces between the sand particles is minimized. The character ofthe sand particles,

Vduct 88 and are held in place and insulated from each other and fromthe walls of the duct by insulating plates 90 through apertures inwhiclrthe ducts are passed. 4The spacing between the buses, and betweenthe buses and duct', is suliicient to prevent flash over in air, andtheduct is-completely filled with sand in the manner described above.

1. A11 electric high tension switching system comprising the combinationof oil im- ,mersed electric switches, high tension buses located intheimmediate vicinity of said oil immersed switches and connectedtherewith, enclosures containing said buses, and electrically insulatingpulverulent mobile bodies of loose discrete, solid insulating iireproofparticles contained in said enclosures about said buses, andconstituting means to prevent access of a conducting gas to said buses.-

2. An electric high tension switching system comprising the combinationof an oil immersed electric switch, a high tension conductor adjacentsaid oil immersed switch, an enclosure for said conductorfand anelectrically insulating mobile body composed of loose discrete solidinsulating fireproof particles contained in said enclosure and about andenclosing said conductor, and constituting means to prevent access of aconducting gas to said conductor.

3.. An electric high tension switching system c omprisingthe combinationof an oil immersed electric switch, a high tension conductor adjacentsaid oil immersed switch,an enclosure for said conductor, and a body ofloose sand'contained in said enclosure and by which said conductor isenclosed, and which constitutes means to shield said high tensionconductor against access of a conducting gas thereto. c

4. An lectric high tension switching system comprising the combinationof an oil immersed electric switch, ahigh tension conductor locatedwithin the zone of switch gases'that may be expelled from said oilimmersed switch, and means to insulate said high tension conductor fromcontact with such gases and also to insulate said conductor electricallyconsisting of a thick mobile mass of small discrete solid insulating andheat resistant particles disposed about andin enclosing relation withsaid conductor at its extent in said gas zone.

5.l An electric high tension `switching system comprising thecombination of an oil immersed electricswitch, 'a high tension buslocated at said switch and havingV a branch connected with a terminal ofsaidoil immersed switch, a duct containing said bus having a branchcontaining said bus-branch, and a mobile insulating body contained insaid duct and the branch thereof and enclosing said bus land its branch,and composed of loose discrete solid insulating particles, andconstituting means to prevent access of a conducting gas to said bus andsaid branch.

6. An electric high tension switching system comprising the combinationof an o1l` immersed electric switch, a high tension bus located'atsaidswitch'andhaving a branch connected with a terminal of said oilimmersed switch, a duct containing said bus having a branch containingsaid bus-branch, and an insulating body contained in said duct and thebranch thereof and enclosing said bus and its branch, and composed ofdiscrete solid insulating particles of sand, and constituting means toprevent access of a conducting gas to said bus and said branch.

7. An electric high tensiony switching system comprising the combinationof a switch,

and .a high tension conductor, and a mobile, insulating,- inert,non-combustible body ot loose solid material enclosing said conductor,

and constituting meansl to prevent access ofv conducting gas to saidhigh tension conductor.

8. In a high tension electric distribution system, the combination of anelectrical apparatus capable of giving off electrically conducting gasand fume, a high tension lconductor associated with said apparatus, anda mobile body of loose particles of insulating, non-combustible solidmaterial enclosing said conductor and isolatingit from said gas andfume.

9. The combination of electrical apparatus capable of "giving offelectrically conducting gas and fume, a high tension'c'onductorassociated with' said apparatus, insulatorsy supporting said conductor,an enclosure for said conductor and insulators, and a mobile body ofinsulating, non-combustible solid material contained in said enclosureabout said conductor and insulators and enclosing both against said gasand fume..

10. The combination of an electric conductor operated at such elevatedpotential that when the conductor is within the inliuence of anelectrically conducting gas a current arc passes through the gas fromthe conductor to a lower potential part, and means to maintain saidconductor out of the influence of such conducting as consisting of anenclosing envelope there or composed largely of vdiscrete particles ofloosely compacted insulating and fireprooil material which is'capablewof lowing,.whereby to occupy voids ,.that may occur, within theIn testimony whereof, I havesigned my name to this specification.

GEORGE A. BURNHAM.

e combination of a high tension con-

